1. Field of the Invention
The present invention relates to printing, and, more particularly, to methods and apparatuses used in guiding a hand-operated printer.
2. Description of the Related Art
A typical desktop ink jet printer is a stationary apparatus that includes a reciprocating printhead carrier that carries a printhead in a main scan direction, and includes a drive roller assembly that advances a print medium, e.g., paper, in a sub-scan direction relative to the printhead. To determine a printhead position relative to a print medium, a typical desktop ink jet printer includes an encoder strip running parallel to the main scan direction for determining the printhead position in the main scan direction, i.e., along the X-axis, and monitors the rotation of the drive roller assembly to determine an amount of print medium feed in the sub-scan direction, e.g., along the Y-axis.
Another type of printer is a hand-operated printer, also sometimes referred to as a hand-held printer or hand printer. In contrast to a desktop printer, a hand-operated printer is moved manually and randomly in its entirety relative to the print medium, such as paper or other surface to be printed, and does not include a drive mechanism for positioning a printhead relative to the print medium. In other words, the hand-operated printer is manually moved over the print medium by way of a motive force exerted via a user's hand.
The hand-operated printer senses the position on the print medium and activates printing whenever the area under the print element matches an unprinted section of a latent image, i.e., the portion of the image yet to be printed. An optical encoder typically is used to provide position feedback of relative motion between the hand-operated printer and the print medium. A hand-operated printer navigates by continually updating its position with calculations of data from sustained sampling of information.
Hand printing requires the printing of multiple swaths of print data over multiple passes of the hand-operated printer over the print medium to complete a document page. The user must overlap these swaths of print so that no portion of the page is unprinted. Failure to overlap the swaths results in leaving a void or print defect on the page. One type of hand-operated printer has guide markings on the side of the printer to indicate generally to the user the location of the print swath in relation to the print medium, but this is better at predicting the start position of print than aligning multiple swaths.